1. Technical Field
This disclosure is generally related to surgery, and more particularly to intravascularly or percutaneously deployed medical devices suitable for determining locations of cardiac features or ablating regions of cardiac tissue, or both.
2. Description of the Related Art
Cardiac surgery was initially undertaken using highly invasive open procedures. A sternotomy, which is a type of incision in the center of the chest that separates the sternum (chest bone) was typically employed to allow access to the heart. In the past several decades, more and more cardiac operations are performed using intravascular or percutaneous techniques, where access to inner organs or other tissue is gained via a catheter.
Intravascular or percutaneous surgeries benefit patients by reducing surgery risk, complications and recovery time. However, the use of intravascular or percutaneous technologies also raises some particular challenges. Medical devices used in intravascular or percutaneous surgery need to be deployed via catheter systems which significantly increase the complexity of the device structure. As well, doctors do not have direct visual contact with the medical devices once the devices are positioned within the body. Positioning these devices correctly and operating the devices successfully can often be very challenging.
One example of where percutaneous medical techniques have been employed is in the treatment of a heart disorder called atrial fibrillation. Atrial fibrillation is a disorder in which spurious electrical signals cause an irregular heartbeat. Atrial fibrillation has been treated with open heart methods using a technique known as the “Cox-Maze procedure.” During this procedure, physicians create lesions in a specific pattern in the left and right atria which block various paths taken by the spurious electrical signals. Such lesions were originally created using incisions, but are now typically created by ablating the tissue with various techniques including radio frequency (RF) energy, microwave energy, laser energy and cryogenic techniques. The procedure is performed with a high success rate under the direct vision that is provided in open procedures, but is relatively complex to perform intravascularly or percutaneously because of the difficulty in creating the lesions in the correct locations. Various problems, potentially leading to severe adverse results, may occur if the lesions are placed incorrectly.
Key factors which are needed to dramatically improve the intravascular or percutaneous treatment of atrial fibrillation are enhanced methods for deployment, positioning and operation of the treatment device. It is particularly important to know the position of the elements which will be creating the lesions relative to cardiac features such as the pulmonary veins and mitral valve. The continuity and transmurality characteristics of the lesion patterns that are formed can impact the ability to block paths taken within the heart by spurious electrical signals.
Several methods have been previously developed for positioning intravascularly or percutaneously deployed medical devices within the heart. For example, commonly assigned U.S. Patent Application Publication 2009/0131930 A1, which is herein incorporated by reference in its entirety, describes a device that is percutaneously guided to a cavity of bodily organ (e.g., a heart). The device can discriminate between fluid within the cavity (e.g., blood) and tissue that forms an inner or interior surface of the cavity (i.e., surface tissue) to provide information or mapping indicative of a position or orientation, or both of the device in the cavity. Discrimination may be based on flow or some other characteristic, for example electrical permittivity or force. The device can selectively ablate portions of the surface tissue based on the information or the mapping. In some cases, the device may detect characteristics (e.g., electrical potentials) indicative of whether ablation was successful. The device includes a plurality of transducer elements that are percutaneously guided in an unexpanded configuration and positioned at least proximate the surface tissue in an expanded configuration. Various expansion mechanisms that include a helical member or an inflatable member are described.
The desire to employ intravascular or percutaneous techniques that employ devices that can fit through catheter sheaths of ever smaller sizes (e.g., on the order of approximately 20-24 French in some cases, 18-20 French in other cases and 16-18 French or less in yet other cases) has increased. In some instances, devices deliverable via larger or smaller sized catheter sheets may be employed. Additional challenges therefore exist in creating a device that can assume an unexpanded configuration for passage through these smaller sheaths and yet, can also assume an expanded configuration suitable for positioning a portion of the device proximate to a tissue surface within the cavity.
The treatment of atrial fibrillation is but one example of a cardiac surgery that requires improved configurable devices. There are many others that require similar improved devices, such as mitral valve repair.
There is a need for enhanced methods and apparatus that allow a portion of a configurable device to assume a delivery or unexpanded configuration suitable for passage though a small bodily opening leading to a bodily cavity, and a deployed or expanded configuration suitable for positioning the portion of the device at least proximate to a tissue that forms an interior surface of the cavity.
There is a need for enhanced methods and apparatus that allow a portion of a configurable device to assume a delivery or unexpanded configuration suitable for passage though a small bodily opening leading to a bodily cavity, and a deployed or expanded configuration suitable for positioning the portion of the device at least proximate to a tissue that forms an interior surface of the cavity, the enhanced methods and apparatus being further suitable for the determination of the relative position of anatomical features within the cavity such as pulmonary veins and a mitral valve with respect to the configurable medical device.
There is a further need for enhanced methods and apparatus that allow a portion of a configurable device to assume a delivery or unexpanded configuration suitable for passage though a small bodily opening leading to a bodily cavity, and a deployed or expanded configuration suitable for positioning the portion of the device at least proximate to a tissue that forms an interior tissue surface of the cavity, the enhanced methods and apparatus being further suitable for treatment of the interior tissue surface. Treatment may include the formation of lesions in a specified position relative to anatomical features within the cavity such as pulmonary veins and a mitral valve.
There is a further need for enhanced methods and apparatus that allow a portion of a configurable device to assume a delivery or unexpanded configuration suitable for passage though a small bodily opening leading to a bodily cavity, and a deployed or expanded configuration suitable for positioning a plurality of transducer elements over a region extending across a majority of an interior tissue surface of the cavity. In particular, there is a need for enhanced methods and apparatus to arrange a plurality of transducer elements in a two- or three-dimensional grid or array capable of mapping, ablating, and or stimulating an inside surface of a bodily cavity or lumen without requiring mechanical scanning.